Electrically powered crosscut saws have been in existence for decades and have been manufactured in many different configurations. In order to improve the productivity and consistency of cut on these saws many manufacturers have added apparatus both pneumatic and electromechanical to automatically cycle the rotating saw blade through the stock. This cut cycle has traditionally been initiated by a foot or knee pedal so that the operator's hands are free to manipulate the stock. While this configuration is effective for the efficient throughput of material through the saw, it does not prevent the operator from accidentally cycling the saw while his hands or arms are in harm's way.
To address this unsafe condition, manufacturers have offered these saws with a two-hand anti-tie down control that prevents the initiation of the cutting cycle unless two buttons spaced far enough apart to prevent one-handed operation are depressed simultaneously.
The logic circuit that monitors these buttons will not initiate the cycle unless both buttons are depressed within a few milliseconds of one another. This logic prevents the operator from defeating the system by tying one button down and then using only one hand to cycle the saw. Hence the name two-hand anti-tie down. This type of control is widely accepted throughout industry as a safe method for initiating a machine cycle.
Since the nature of the two-hand anti-tie down circuit is to ensure that the operator's hands are safely away from the process to prevent injury, their use on automatic saws prevents the operator from being able to hold the stock against the saw's fence while the cut is being performed. So in order to effectively implement this safety feature, manufacturers must add pneumatic clamping to the saw thereby adding significant cost and complexity to the product as well as reducing the throughput due to added motion on behalf of the operator.
From the foregoing, it can be seen that a need exists for further enhancements to the implementation of two-hand anti-tie down systems onto automatic saws in order to meet today's more rigorous safety requirements while maintaining or improving usability and productivity of the products.